This invention relates to slide fasteners, and more particularly to a slide fastener with a pair of stringers which are normally separated completely from each other by pulling a slider down along rows of interlocking fastener elements to a separable bottom end fitting on the stringers but which, in an emergency, can be readily separated from the top ends thereof without moving the slider to the bottom end fitting and hence without manipulating the latter. The emergency opening fastener of this character finds typical application on sleeping bags or tents.
In the slide fastener of the type under consideration, it has been common to remove the cord, which is stitched to each stringer tape to provide the usual edge bead, from an upper end portion of one of the tapes so that the upper end portion of the tape may be smoothly withdrawable from the slider in an emergency. It is, however, a rather difficult and time-consuming job to cut off only the cord from the tape without damaging the latter. Moreover, after removal of the cord from the upper end portion of the tape, there usually remain loose threads or yarns used for stitching the cord. Such loose threads, and possibly the threads that have revaled from the damaged zone of the tape, may be caught by the slider while the upper end portion of the tape is being withdrawn therefrom in an emergency, thereby preventing the smooth separation of the fastener stringers.
It has also been known to cover the beaded edge of the upper end portion of one of the stringer tapes with a sheet of thermoplastic material and then to flatten the edge with the thermoplastic sheet under application of heat and pressure. This measure has been resorted to particularly in the case where the edge bead of the tape is formed by a cord woven or knitted therein and is therefore not removable without damaging the tape. The tape edge thus flattened, however, is easy to regain the original thickness when moistened or by being repeatedly bent or folded in the use of the fastener, so that the tape is likely to become not easily withdrawable from the slider.